This invention relates to portable vacuum cleaners, and especially to the type generally referred to as "wet/dry" vacuum cleaners, which are capable of picking up not only solid matter, such as dust, dirt and other dry debris, but also liquid or semiliquid material. More particularly, the invention relates to a unique means for interrupting the suction when the liquid level in a collector tank reaches a predetermined level. This prevents the liquid from being drawn into the vacuum blower intake and from contacting the filter normally interposed between the vacuum blower air inlet and the collection tank.
Wet/dry-type vacuum cleaners are used for a variety of purposes, such as the extraction of liquid used in the cleaning of floors, carpets, upholstery, etc. In these vacuum units, the liquid is sucked into a tank through a vacuum hose, and thus it accumulates progressively in the collection tank during the operation. In order to prevent the liquid from rising above a predetermined level limit where it could overflow, block a blower inlet, damage a dust filter, etc., it is advantageous to provide a device that interrupts the air flow producing the suction, and thus prevents further liquid accumulation.
In prior art devices, this requirement has been met in several ways, such as by using a float-operated control mechanism that opens a switch to turn off the vacuum blower motor. Another means involves the use of a sphere-shaped rising float that will, upon reaching a certain height, engage an air flow port or inlet to block further flow of air to the blower.
There techniques and others, however, have certain deficiencies and disadvantages. A float-operated switch is often unreliable, particularly since a failure of the float, the float linkage, or the switch itself will result in an overflow. A float, such a sphere or ball-shaped device that rises to sealing engagement with an air inlet is often not shaped properly, and may not achieve a complete seal. Also, the float may become punctured and fill with liquid.
The device of the present invention, however, resolves many of the difficulties indicated above and affords other features and advantages heretofore not obtainable.